Mechanisms Of Palladium And Nickel Catalyzed Cross Coupling Reactions

Transition-metal catalyzed cross-coupling reactions are indispensible tools in modern synthetic chemistry.C-C,C-O,and C-N bonds can be readily formed via cross-coupling reactions.Among cross-coupling reactions,Suzuki,Negishi,Kumada, Stille,etc.are important name reactions.Research in this field has achieved much, including Fu and Buchwald's catalyst that can activate PhCl,Shi and Garg's recent report about C-O activation of aryl esters.However,the scale and selectivity of these reactions still need to be improved,which rely on more information about reaction mechanisms.In this study,we employ theoretical calculations to study the mechanisms of new cross-coupling reactions.In the first chapter,we reviewed the important cross-coupling reactions.We also introduce the goal and creativity of this thesis.In the second chapter,several computational methods were introduced,including ab initio methods,density functional methods(DFT),and ONIOM method. Furthermore,we benchmarked a series of common DFT methods and establish reliable DFT method for Pd and Ni compounds.In the third chapter,we employed DFT method augmented with polarized continuum model to study the oxidative addition of PhCl and PhBr to Pd(PR₃)₂ (R=Me,Et,i-Pr,t-Bu and Ph).The real active intermediate of oxidative addition is monophosphine PdPR₃,and its concentration governs the activity of the catalyst.In the fourth chapter,the mechanism of the cross-coupling of aryl esters and boronic acids were studied and established.Furthermore,the reason for the selective activation on the stronger C-O bond is elucidated.In this dissertation,we use computational chemistry tools to study the mechanisms of Pd and Ni catalyzed reactions.We explained experimental observations and provide insights to the scale and selectivity for the design of new catalysts.